Apoptosis is of fundamental importance to biological processes including embryogenesis, maintenance of tissue homeostasis, normal cellular development of multicellular organisms, elimination of virus-infected cells, and the development of immune system. It is a type of death that is fundamentally distinct from degenerative death or necrosis in that it is an active process of gene-directed cellular self-destruction which, in some instances, serves a biologically meaningful homeostatic function. Necrosis, in contrast, is cell death occurring as a result of severe injurious changes in the environment of infected cells.
Morphologically, apoptosis is characterized by the rapid condensation of the cell with preservation of membranes. Synchronistically with the compaction of chromatin, several biochemical changes occur in the cell. Nuclear DNA is cleaved at the linker regions between nucleosomes to produce fragments that are easily demonstrated by agarose gel electrophoresis wherein a characteristic ladder develops.
The primary image of apoptosis is that of the dying thymocyte: fusion of chromatin into one mass, which binds to the nuclear membrane, while the cytoplasm remains apparently intact before beginning to condense. The nuclear change is one of the earliest visible processes; the conversion to the condensed state occurs rapidly and is accompanied by endonucleolytic degradation of DNA between nucleosomes. Once the chromatin has condensed, electrophoresis of the DNA demonstrates a ladder of fragments differing in size by 180 bp, generated by an enzymatic activity resembling that of DNase I.
This type of cell death is seen in many varieties of cells, especially those that, like lymphocytes or thymocytes, have relatively little cytoplasm and are highly mitotic or derive from highly mitotic lines. In this situation, in which mitotic cells are likely to face challenges by mutagens (viruses, toxins), an appropriate biological imperative would be to destroy the DNA rapidly and effectively. Thus, this type of cell death is particularly dramatic among hematopoietic cells and their derivatives.
Several regulatory components of the apoptotic pathway have been identified in various living organisms including man and the nematode Caenorhabditis elegans. 
Two murine transcription products involved in cell apoptosis have been reported by Inohara et al. (1998), that have been named respectively CIDE-A and CIDE-B. Murine CIDE-A and CIDE-B have strong homology with the murine anti-apoptosis DFF45 protein as well as with the drosophila protein DREP-1. The homology of CIDE-A, CIDE-B and FSP27 with DFF45 was restricted to an N-terminal region designated by Inohara et al. as CIDE-N domain which showed 39, 29 and 38% amino acid identity respectively with DFF45.
Because there is a strong need in the art to make available to the public novel means useful to prevent or inhibit apoptosis disorders, either in the case of disorders caused by abnormal cell proliferation wherein apoptosis induction is desirable or in the case of disorders caused by abnormal cell death wherein an inhibition or an arrest of apoptosis is desirable, the inventors have attempted to isolate and characterize a novel gene encoding a protein involved in apoptosis pathway, namely the human CIDE-B gene.